This invention relates to an accumulator-dehydrator assembly for an air conditioning system. This invention specifically relates to an accumulator-dehydrator having a J-tube with an expansion chamber as part of the J-tube and a column separation feature as part of the J-tube.
Vehicle air conditioning systems include a compressor that compresses and superheats refrigerant, which then runs through a condenser, expander and evaporator in turn before returning to the compressor to begin the cycle again. Mixed in with the refrigerant is a small amount of lubricating oil which is entrained within the refrigerant and is needed to ensure smooth performance of the compressor and to prolong the life of the compressor.
Interposed between the evaporator and compressor is an accumulator-dehydrator which is designed to accomplish several objectives. The accumulator-dehydrator primarily receives and accumulates the evaporator output effluent. The accumulator-dehydrator serves as a reservoir or separator in which fluid collects at the bottom and vapor at the top. The accumulator ensures that only refrigerant in a vapor stage passes to the compressor. The accumulator-dehydrator also prevents a liquid slug from being pulled or sucked into the downstream compressor. Still further, a desiccant is typically located in the bottom of the accumulator-dehydrator to absorb any water in the refrigerant.
Traditionally accumulator-dehydrators are known to use a U-shaped or
J-shaped tube more commonly known as a J-tube to collect liquid. The accumulator-dehydrator includes a canister with an inlet connected to the evaporator. The refrigerant enters the inlet as a vapor and liquid mixture. The liquid drops to the bottom of the canister and the vapor rises to the top. The J-tube is connected at one end to the canister outlet, which in turn is connected to the compressor. The J-tube extends down from the outlet to near the bottom of the canister and then turns upward and extends to near the top of the canister. The free end of J-tube, the portion near the canister top, is open to allow the vapor to be drawn into the J-tube and exit to the outlet to the compressor. A small opening is provided in the bottom turn-portion or U-portion of the J-tube to allow the liquid including the oil, to enter the J-tube and be entrained and delivered with the vapor to the compressor.
With traditional J-tube accumulator-dehydrators and the compressor disengaged (no flow through the J-tube), the J-tube will fill with liquid to the same level as the liquid in the canister. When the compressor is engaged a large pressure differential quickly occurs across the liquid stored in the J-tube. The large pressure differential causes the liquid in the J-tube to accelerate rapidly and to violently boil off. This rapid liquid acceleration and boiling imparts energy to the accumulator-dehydrator, which is classified as xe2x80x9cbumpxe2x80x9d energy. This xe2x80x9cbumpxe2x80x9d energy is present in all traditional J-tube accumulator-dehydrators. This energy manifests itself as a broad frequency noise known as the xe2x80x9cbumpxe2x80x9d.
The energy imparted to the accumulator-dehydrator is a function of the rate of pressure drop across the liquid level in the J-tube within the accumulator-dehydrator. The pressure drop is affected by the compressor displacement, compressor drive ratio, and the amount of internal volume on the suction side of the accumulator-dehydrator. The magnitude and occurrence of noise is dependent on the total energy imparted to the accumulator-dehydrator, the accumulator-dehydrator lines and the extent of accumulator-dehydrator isolation.
The accumulator-dehydrator of the present invention has a modified J-tube which contains an expansion chamber. The expansion chamber is a bulge on the J-tube with a predetermined volume. The expanded portion of the lower end of the expansion chamber starts at a point above the liquid line in the modified J-tube.
As part of the J-tube there is also a section of side wall which protrudes towards the center of the expansion chamber of the J-tube. This protrusion is called the column separation feature. The column separation feature directs any fluid moving through the J-tube into the expansion chamber. The column separation feature further helps eliminate any liquid slug from being expelled from the accumulator-dehydrator.
When the compressor starts its cycle and begins to draw refrigerant into the compressor the expansion chamber in the J-tube lengthens the time of the pressure drop upon engagement of the compressor. The velocity of the liquid extracted from the J-tube is decreased and the liquid begins to boil or flash much easier because the expansion chamber provides for more room and a lower pressure.
In the preferred embodiment, the accumulator-dehydrator of the present invention uses a J-tube, which is manufactured out of plastic. This allows for economical and cost effective manufacturing.